WO2008111816A1

WO2008111816A1 - Multi-band antenna and board for the same

Info

Publication number: WO2008111816A1
Application number: PCT/KR2008/001439
Authority: WO
Inventors: Byung Hoon Ryou; Won Mo Sung; Chang Ho Hong
Original assignee: E.M.W. Antenna Co., Ltd.
Priority date: 2007-03-15
Filing date: 2008-03-14
Publication date: 2008-09-18
Also published as: KR20080084200A; KR100875837B1

Abstract

There is herein disclosed a multi-band antenna with enhanced gain and sensitivity by improving isolation between antenna elements. The multi-band antenna in accordance with the present invention includes a first antenna unit including a first feed element connected to a feed unit of the antenna and a first antenna element electrically connected to the first feed element, the first antenna element being adapted to resonate at a first frequency band, a second antenna unit including a second feed element connected to the feed unit of the antenna and a second antenna element electrically connected to the second feed element, the second antenna element being adapted to resonate at a second frequency band, and an isolation unit disposed between the first feed element and the second feed element and electrically connected to a ground surface of the antenna, the isolation unit being formed of a conductive material. Thus, isolation between the first antenna unit and the second antenna unit is improved through the isolation unit. Ac¬ cordingly, according to the present invention, isolation between antennas can be improved, and a phenomenon in which one antenna acts on the other antenna as a noise source, thus degrading gain and sensitivity, can be prevented.

Description

MULTI-BAND ANTENNA AND BOARD FOR THE SAME Technical Field

[1] The present invention relates to a multi-band antenna, and more particularly, to a multi-band antenna with enhanced gain and sensitivity by improving isolation between antenna elements through improvement of a structure. Background Art

[2] In general, an antenna is used in mobile communication terminals such as mobile phones. The antenna is disposed at the outside or the inside of a terminal main body so as to transmit/receive necessary information to/from external devices wirelessly.

[3] In mobile communication terminals, this antenna is constructed in the form of a helical antenna or a dipole antenna, so that an external antenna protruding outwardly from the communication terminal has been used.

[4] The external antenna is advantageous in a nondirectional radiation characteristic, but is disadvantageous in that it is highly likely to be broken by external force since the antenna protrudes outwardly and very inconvenient to carry. Further, the external antenna is problematic in designing a beautiful external appearance of a terminal.

[5] To solve the problems of the external antenna, an internal antenna, which does not protrude outwardly and is embedded within a terminal, has been developed.

[6] However, in general, the internal antenna is disadvantageous in that it has a bandwidth narrower than that of the external antenna. Thus, a multi-band antenna has also been used in which one or more antenna elements are applied to one carrier so as to expand the bandwidth or implement the multi-band.

[7] In such a multi-band antenna, as the mobile communication terminals are miniaturized, it is difficult for two or more antenna elements to ensure a sufficient isolation distance (1/2 of a wavelength). A problem arises because isolation between the antenna elements is not secured.

[8] Like this, if isolation between the antennas is not secured, one antenna acts as a noise source with respect to another antenna, contributing to degradation in gain and sensitivity. It results in a deterioration of a specific absorption rate (SAR) characteristic due to the interaction of two antenna elements. Disclosure of Invention

Technical Problem

[9] Accordingly, the present invention has been made to overcome the above- mentioned problems occurring in the prior art, and it is an object of the present invention to provide a multi-band antenna which improves isolation between a plurality of antenna elements in a limited space.

[10] It is another object of the present invention to provide a multi-band antenna having enhanced gain and sensitivity and a reduced SAR. Technical Solution

[11] To accomplish the above objects, according to one aspect of the present invention, there is provided a multi-band antenna, including a first antenna unit including a first feed element connected to a feed unit of the antenna and a first antenna element electrically connected to the first feed element, the first antenna element being adapted to resonate at a first frequency band, a second antenna unit including a second feed element connected to the feed unit of the antenna and a second antenna element electrically connected to the second feed element, the second antenna element being adapted to resonate at a second frequency band, and an isolation unit disposed between the first feed element and the second feed element and electrically connected to a ground surface of the antenna, the isolation unit being formed of a conductive material.

[12] Further, the ground surface of the antenna may be formed on a main board of an apparatus. A part of a main board may include a connecting portion to which the isolation unit is electrically connected, the connecting portion being is formed in a specific pattern.

[13] The isolation unit may have a specific width and extend, between the first feed element and the second feed element.

[14] According to another embodiment of the present invention, the isolation unit is provided on an external casing covering the antenna and is electrically connected to the ground surface of the antenna when the external casing is assembled. The isolation unit may include an electromagnetic interference (EMI) shielding material.

[15] To accomplish the above objects, according to another aspect of the present invention, there is provided a board for a multi-band antenna, including a first feed element connected to a feed unit of the antenna, the first feed element being connected to a first antenna element resonating at a first frequency band, a second feed element connected to the feed unit of the antenna, the second feed element being connected to a second antenna element resonating at a second frequency band, and an isolation unit disposed between the first feed element and the second feed element and electrically connected to a ground surface of the antenna, the isolation unit being formed of a conductive material.

Advantageous Effects

[16] The multi-band antenna according to the present invention has the following advantages. [17] First, the multi-band antenna including the plurality of antenna elements includes the isolation unit connected to the ground surface between the antennas. Accordingly, there is an advantage in that mutual interference between the antennas can be minimized although a sufficient isolation distance is secured between the antennas.

[18] Second, an internal antenna is limited to ensure an isolation distance since it must be accommodated within one casing. However, according to the present invention, the isolation unit is disposed between the antennas, so one antenna acts as a noise source of another antenna. Accordingly, there is an advantage in that a decrease in gain and sensitivity of an antenna can be minimized.

[19] In particular, the isolation unit is constructed in a ground form between antennas using an electromagnetic interference (EMI) shielding material used to shield harmful electromagnetic waves. Therefore, isolation between the antennas can be improved through a simple method, gain and sensitivity can be enhanced, and the SAR can be decreased.

[20] Third, since the isolation unit is provided between antennas, a necessary space can be minimized while meeting gain and sensitivity required by an antenna including a plurality of antenna elements. Accordingly, there is an advantage in that the size of various devices built in the antenna can be minimized. Brief Description of the Drawings

[21] FIG. 1 is a plan view showing a board for a multi-band antenna in accordance with a first embodiment of the present invention;

[22] FIG. 2 is a plan view showing a multi-band antenna in accordance with a second embodiment of the present invention;

[23] FIG. 3 is an upper perspective view of FIG. 2; and

[24] FIG. 4 is a perspective view showing a multi-band antenna in accordance with a third embodiment of the present invention. Best Mode for Carrying Out the Invention

[25] Reference will now be made in detail to a preferred embodiment of the present invention with reference to the attached drawings. In describing the present embodiments, the same terms and reference numbers will be used to refer to the same parts and additional description thereof is omitted.

[26] The construction of a multi-band antenna in accordance with a first embodiment of the present invention is described below with reference to FIG. 1.

[27] A board for the multi-band antenna in accordance with the present invention includes a first feed element, a second feed element and an isolation unit connected to a feed unit of the antenna.

[28] First, the first feed element 132 is connected to the feed unit (not shown) of the antenna and is connected to a first antenna element (not shown). [29] Here, the feed unit of the antenna can be formed on a main board 110 in which a number of electronic components are mounted. The first feed element 132 is connected to the feed unit of the antenna. The first feed element 132 is provided on the main board 110 in the form of a terminal, as shown in FIG. 1, so that it can be electrically connected to the first antenna element.

[30] The first antenna element is electrically connected to the first feed element 132 formed on the main board 110 and is supplied with power. The first antenna element is constructed to resonate at a first frequency band.

[31] The shape or type of the first antenna element is not limited and can be decided in various ways according to a desired frequency band. That is, the first antenna element can be formed to have a specific pattern according to a desired frequency band around the board or an external casing. Here, it is to be understood that the shape, size, etc. of the first antenna element can be changed so that the first antenna element can resonate at a specific proper frequency band.

[32] The second feed element is also connected to the feed unit of the antenna and connected to a second antenna element (not shown), similar to the first feed element.

[33] In the present embodiment, the second feed element 152 can also be provided on the main board 110 in the form of a terminal in the same manner as the first feed element 132 so that it can be electrically connected to the second antenna element.

[34] Furthermore, the second antenna element is electrically connected to the second feed element 152 formed on the main board 110 and supplied with power. The second antenna element is constructed to resonate at a second frequency band.

[35] The isolation unit 170 is a constituent element provided between the first feed element 132 and the second feed element 152 and connected to a ground surface of the antenna. Here, the ground surface of the antenna can be provided in various forms. The present embodiment illustrates a form in which the main board 110 forms the ground surface.

[36] As described above, an internal antenna cannot ensure a sufficient isolation distance because a first antenna unit and a second antenna unit must be accommodated within the casing of a terminal. Thus, one antenna acts as a noise source of the other antenna, resultantly causing to decrease gain and sensitivity of the antenna.

[37] According to the present invention, the isolation unit 170 connected to the ground surface is disposed between the feed units of the first and second antenna elements, resonating at different frequency bands, in order to minimize mutual interference between the antenna elements.

[38] In experiments carried out by the present inventors, in the case in which the main board 110, forming the ground surface, and the isolation unit 170 are electrically connected to each other and the isolation unit 170 is disposed between the feed elements 132, 152, it was found that mutual interference was reduced significantly and the SAR was decreased.

[39] The isolation unit 170 is formed from conductive material. In the present embodiment, in order to electrically connect the isolation unit 170 and the main board 110 forming the ground surface, a connecting portion 12 having a specific pattern is formed in part of the main board 110. The connecting portion 112 connects the isolation unit 170 and the main board 110, so that the isolation unit 170 is grounded.

[40] Furthermore, the isolation unit 170 according to the present embodiment has a shape having a specific width and extending in the length direction between the first feed element 132 and the second feed element 152, as shown in FIG. 1.

[41] The isolation unit 170 can employ a variety of material, that is, electrical conductors. For example, in general, the isolation unit 170 can be made of gold mesh.

[42] The construction of a multi-band antenna in accordance with a second embodiment of the present invention is described below with reference to FIGS. 2 and 3.

[43] The multi-band antenna according to the present embodiment includes a first antenna unit 230 having a first feed element 232 and a first antenna element 234, a second antenna unit 250 having second feed elements 252,256 and second antenna elements 254,258, and an isolation unit 270 provided between the first feed element 232 and the second feed elements 252,256 and connected to a ground surface (not shown).

[44] In the present embodiment, in the first antenna unit 230 and the second antenna unit

250, the feed elements 232, 252 and 256 and the antenna elements 234, 254 and 258 are not formed from separate elements and are integrated without being connected to each other.

[45] That is, in the first antenna unit 230 and the second antenna unit 250 of the present embodiment, as shown in FIG. 2, each of the first and second feed elements 232, 252 and 256 has a square plate shape. Furthermore, each of the first and second antenna elements 234, 254 and 258 has a width smaller than that of each of the feed elements 232, 252 and 256 and extends. Each of the first and second antenna elements 234, 254 and 258 has a specific pattern and is formed outside a carrier 220, as shown in FIG. 3.

[46] Furthermore, the isolation unit 270 is provided between the first feed element 232 and the second feed elements 252, 256 and prevents mutual interference between the first antenna unit 230 and the second antenna unit 250.

[47] Although not shown in the drawings, even in the present embodiment, the isolation unit 270 is electrically connected to the ground surface and substantially functions as a ground surface between the antenna units 230,250.

[48] Furthermore, a fixing member 222 for fixing an upper portion of the isolation unit

270 is formed on the carrier 220, so that the isolation unit 270 can be fixed on the carrier 220.

[49] Meanwhile, according to the present embodiment, in the second antenna unit 250, each of the second feed elements 252, 256 and the second antenna elements 254, 258 forms a pair so that radiation can be performed at a high frequency band and a low frequency band, respectively.

[50] In the present embodiment, the first antenna unit 230 is set to receive the frequency band of about 1500 MHz for reception of a global positioning system, and the second antenna unit 250 is set to receive a low frequency band of 800 to 900 MHz for reception of voice and a high frequency band of 1720 to 2170 MHz.

[51] The construction of a multi-band antenna in accordance with a third embodiment of the present invention is described below with reference to FIG. 4.

[52] The multi-band antenna in accordance with a third embodiment of the present invention includes a first antenna unit 330 having a first feed element 332 and a first antenna element 334, a second antenna unit 350 having a second feed element 352 and a second antenna element 354, and an isolation unit 370 provided between the first feed element 332 and the second feed element 352 and connected to a ground surface (not shown), similar to the first and second embodiments.

[53] Meanwhile, in the present embodiment, as shown in FIG. 4, the isolation unit 370 is provided on an external casing 310 covering an antenna.

[54] The isolation unit 370 is electrically connected to the ground surface of the antenna when the external casing 310 is coupled to the board where the first antenna unit 330 and the second antenna unit 350 are formed. Furthermore, the isolation unit 370 according to the present embodiment is formed by coating an EMI shielding material E.

[55] In general, the EMI shielding material is coated as paints on an inner surface of the external casing 310 or an outer surface of the board in such a way as to electrically connect to the ground surface of the board. Thus, the EMI shielding material functions to prevent external harmful electromagnetic waves, introduced into the terminal main body, from having a bad influence on electronic components.

[56] In the present embodiment, as described above, the EMI shielding material E for shielding harmful electromagnetic waves is used as the isolation unit 370 for isolating the antenna units 330, 350. More specifically, the EMI shielding material E is coated on the inner surface of the external casing 310. In particular, the isolation unit 370 having the EMI shielding material E coated thereon is disposed between the first feed element 332 and the second feed element 352. Thus, when the external casing 310 is coupled to the board, the isolation unit 370 is electrically connected to the ground surface on the board, so that the isolation unit 370 functions to significantly reduce mutual interference between the antennas. [57] FIG. 4 illustrates a construction in which the isolation unit is constructed in a barrier rib form at a location corresponding to the portion between the first feed element 332 and the second feed element 352 on the inner surface of the external casing 310.

[58] Meanwhile, concrete shapes of the first and second antenna elements 334, 354 may be modified in various ways according to a desired frequency band or a design condition.

[59] The preferred embodiments in accordance with the present invention have been described above. It will be apparent to those skilled in the art that the present invention can be implemented to have other specific forms without departing from the scope and spirit of the invention, other than the above-described embodiments.

[60] Therefore, the above-described embodiments should be construed to be illustrative and therefore the present invention is not limited to the above description, but may be modified within the scope of the appended claims and equivalent thereof.

[61]

Claims

[ 1 ] A multi-band antenna comprising: a first antenna unit including a first feed element connected to a feed unit of the antenna and a first antenna element electrically connected to the first feed element, the first antenna element being adapted to resonate at a first frequency band; a second antenna unit including a second feed element connected to the feed unit of the antenna and a second antenna element electrically connected to the second feed element, the second antenna element being adapted to resonate at a second frequency band; and an isolation unit disposed between the first feed element and the second feed element and electrically connected to a ground surface of the antenna, the isolation unit being formed of a conductive material.

[2] The multi-band antenna as defined in claim 1, wherein the ground surface of the antenna is formed on a main board of an apparatus.

[3] The multi-band antenna as defined in claim 1, wherein a part of a main board includes a connecting portion to which the isolation unit is electrically connected, the connecting portion being is formed in a specific pattern.

[4] The multi-band antenna as defined in claim 1, wherein the isolation unit has a specific width and extends, between the first feed element and the second feed element.

[5] The multi-band antenna as defined in claim 1, wherein the isolation unit is provided on an external casing covering the antenna and is electrically connected to the ground surface of the antenna when the external casing is assembled.

[6] The multi-band antenna as defined in claim 1, wherein the isolation unit comprises an electromagnetic interference (EMI) shielding material.

[7] A radio communication apparatus comprising an antenna according to any one of claims 1 to 6.

[8] A board for a multi-band antenna comprising: a first feed element connected to a feed unit of the antenna, the first feed element being connected to a first antenna element resonating at a first frequency band; a second feed element connected to the feed unit of the antenna, the second feed element being connected to a second antenna element resonating at a second frequency band; and an isolation unit disposed between the first feed element and the second feed element and electrically connected to a ground surface of the antenna, the isolation unit being formed of a conductive material. [9] The board for a multi-band antenna as defined in claim 8, wherein the ground surface of the antenna is formed in the board. [10] The board for a multi-band antenna as defined in claim 8, wherein the isolation unit has a specific width and extends, between the first feed element and the second feed element. [11] The board for a multi-band antenna as defined in claim 8, wherein the isolation unit comprises an EMI shielding material. [12] A radio communication apparatus comprising a board according to any one of claims 8 to 11.